Appendix A: Antiretroviral Drugs

Preface

This section includes charts of the different classes of antiretroviral drugs, including experimental drugs. Don't be confused by the multiple names for each drug. When a new drug is first developed, the maker gives it a code name. Reports of the earliest test-tube experiments almost always use the code name of the new drug. Often, people hear about new drugs by the code names or a shortened version of the code name, like DMP-266. As development continues, the drug gets a generic name, in this case, efavirenz. Finally, when the maker is ready to sell the new drug, it is given a brand name. Sometimes the brand name varies from one country to another. For example, in North America, the brand name for efavirenz is Sustiva. In other parts of the world, efavirenz is sold as Stocrin. After about 20 years, the company that developed the drug will lose its patent (exclusive rights to make the drug) and other companies are allowed to make their own generic versions of the drug. You'll notice that in most CATIE publications, we use the generic name. In some cases, however, the brand name is more commonly used by people.

Entry Inhibitors and Fusion Inhibitors

Drugs known as entry inhibitors and fusion inhibitors are being developed to prevent HIV from getting into cells. Entry inhibitors are designed to block the receptors HIV uses to attach itself to cells. Fusion inhibitors prevent the virus from fusing with the cell.

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• T-20 (enfuvirtide, Fuzeon) is the only fusion inhibitor approved in Canada. T-20 attaches to gp41 C one of the proteins on the outer shell of HIV C and prevents the virus from fusing with the cell. T-20 is taken as a twice-daily injection subcutaneously (under the skin).

Reverse Transcriptase Inhibitors

Reverse transcriptase inhibitors (RTIs) inhibit (slow down or stop) the action of the reverse transcriptase enzyme. These drugs work to prevent the viral RNA from being converted into DNA. If the viral RNA is not converted to DNA, it cannot become part of the cell. There are three classes of RTIs:

• nucleoside analogue reverse transcriptase inhibitors are often called "nukes" for short. You may also see them called "NRTIs" or just "nucleosides."

• nucleotide analogue reverse transcriptase inhibitors are referred to as "nucleotide RTIs." These drugs work the same way as nukes, but they require one less processing step (called phosphorylation) in the body.

• non-nucleoside reverse transcriptase inhibitors are usually called "non-nukes" or "NNRTIs."

All three classes of drugs target the same enzyme, but their molecular structure is very different and they work in different ways.

Nukes or NRTIs (Approved in Canada)

Nucleotide RTI (Approved in Canada)

Non-Nukes or NNRTIs (Approved in Canada)

Integrase Inhibitors

Integrase goes to work after the reverse transcriptase enzyme has converted viral RNA into DNA. The integrase enzyme inserts the new viral DNA into the DNA of the host cell. For several years, scientists have been trying to develop drugs to block the action of this enzyme. So far, they have had little success.

Protease Inhibitors

Protease inhibitors interfere with the action of the protease enzyme. These drugs prevent protease from cutting the newly made viral proteins into functional parts.

Protease Inhibitors (Approved in Canada)